Geometrical magnetothermopower in n- and p-type InSb -: art. no. 035209

In a previous paper [Heremans et al., Phys. Rev. Lett. 86, 2098 (2001)] we reported how the geometry of a sample of lightly p-type InSb can be manipulated to create a very large change of the thermoelectric power with magnetic field, That effect was called the geometrical magnetothermopower (GMT). In this paper, we review and extend the results in p-type InSb, and present a study of the GMT in n-type InSb. We conclude that, in semiconductors with two types of carriers of different mobilities, the GMT effect makes the thermopower change from being dominated by a high-mobility carrier at zero magnetic field to being dominated by a low-mobility carrier at high field, even when the low-mobility carrier is the minority carrier. We complete the study of the reciprocity relations in macroscopic two-contact thermoelectric systems by adding to the experimental verification of the Kelvin relation the new observation that the GMT is an even function of magnetic field, even in asymmetric geometries. Finally, we model the GMT in both n- and p-type InSb using classical transport theory, and show how this model predicts that the GMT effect can lead to an increase of the thermoelectric power factor, and of the figure of merit, by over 80%.